1. Field of the Invention
The present invention relates to a router and an address identification information management server, and more specifically to an access router (hereinafter referred to as an AR) for relaying a received packet, a border router (hereinafter referred to as a BR) for functioning as a border relay device among networks, and a address identification information management server for use with them.
2. Description of the Related Art
As a conventional technology, the network address translator (NAT) is described in Non-patent Document 1 as having the function of rewriting a source address of a packet in a router having the function of transferring a packet. Additionally, as a derivative technology, Twice NAT is described in Non-patent Document 2 for rewriting not only the source address of a packet but also the destination address of the packet.
The Twice NAT rewrites not only the source address of a packet in the NAT but also the destination address of a packet according to the address conversion table set in a cache table in advance when there arises a conflict between an IP address used in a private network and an IP address used in an external network. However, in the above-mentioned conventional technologies, the address conversion is performed according to the address conversion table statically stored in the router in advance. Therefore, an address conversion table cannot be dynamically generated or an address cannot be rewritten by referring to the table, and addresses before and after conversion cannot be discriminated corresponding to dynamic address conversion, thereby failing in realizing an address conversion network.
Patent Document 1 has disclosed the technology of discriminating an IPv6 (Internet Protocol version 6) address from an IPv4 (Internet Protocol version 4) address based on the address format.
(Patent Document 1)
Japanese Patent Lad-Open No. 2003-18185 (Paragraph 0028-0071)
(Non-Patent Document 1)
Egevang, K. and P. Francis, “The IP Network Address Translator (NAT)”, RFC 1631, May 1994.
(Non-Patent Document 2)
Srisuresh, P. and M. Holdrege, “IP Network Address Translator (NAT) Terminology and Considerations”, RFC 2663, August 1999.
In the conventional study of realizing an address conversion network, when any apparatus in an address conversion network refers to the address of a packet, there is no method of correctly determining whether the address is a terminal identification address for use in an address conversion network, an address of packet transfer, or an address of an IP communications terminal in an external IP network. Accordingly, there have been the problems that the load of the AR having the function of transferring a packet, the BR functioning as a border relay device, and the address management server has been increasing due to unnecessary inquiries about addresses, there occurs a packet loss, an increasing delay of a packet transfer, etc, by an unnecessary inquiry to the address management server.